Nitridation techniques using a nitrogen plasma have been widely studied for application to integrated electronics devices such as gate insulators of metal oxide semiconductor field effect transistors.
For example U.S. Pat. No. 7,619,356 describes an anode for an OLED device wherein the anode comprises an Indium Tin Oxide (ITO) film on a glass substrate and the ITO surface is being treated in a plasma treatment at low pressure (14 mTorr) at 50 W power for 5 minutes. As a result of this treatment 13.3% nitrogen atoms are observed from the surface, which amount corresponds to about 275 oxygen atoms.
U.S. Pat. No. 7,132,373 discloses a method for producing a crystalline metal oxide film (for example a film containing ITO) using a nitrogen or oxygen plasma at a low pressure (50-100 Pa) for at least 3 minutes.
U.S. Pat. No. 7,898,082 discloses a semiconductor device having a barrier metal nitride layer, the layer formed using a nitrogen plasma at high temperatures of 350-750 degrees Celsius.
Furthermore, Nakae et al describes in the Journal of Applied Physics 101, 023513 (2007) the grow models of silicon nitride ultrathin films fabricated using atmospheric pressure plasma on Si-wafers. In case of nitridation with an RF plasma this was done at a low gas pressure of 1.0*10−5 Torr.
JP 4 249 520 discloses the improvement of using a nitridation step with an Argon and Nitrogen plasma treatment at low pressure.
In many manufacturing processes involving glass substrates, such as the process of manufacturing OLED devices, there is a desire to replace glass substrates with low weight, flexible polymeric substrates using polymers with a very thin amorphous layer of metal oxide with improved barrier properties.
It is an object of the invention to provide a method for creating an improved barrier on a substrate, in particular a flexible substrate.